Every other day, Kali D'Angelo is a normal sixteen-year-old girl. She goes to public high school. She attends pep rallies (reluctantly). She's human. And every other day in between . . . she's not.

Though she's not quite sure what she is on those days, Kali knows what she does . . . she hunts, traps, and kills demons, hellhounds, and other supernatural creatures that threaten her world. On those days, she is practically indestructible.

But when Kali notices a mark on a popular girl at school, she knows instantly that the girl is marked for death by an unworldly being. And she knows she has only twenty-four hours to save her.

There's only one problem . . . it's the wrong twenty-four hours.